Downhole anchoring tools include a wellbore anchor for use in firmly fixing a whipstock and similar equipment in the wellbore during sidetracking or lateral drilling operations, also known as “wellbore departure” operations. Here, wellbore anchoring systems may be used to anchor drilling equipment downhole in order to permit certain wellbore operations. Once a main wellbore has been drilled, it is often necessary or desired to drill one or more additional boreholes that branch off, or deviate, from the main wellbore. Such lateral boreholes are typically directed toward different parts of the surrounding formation, with the intent of increasing the output of the well. The main wellbore can be vertical, angled or horizontal. Wellbore departure technology can be applied to both new and existing wells.
In order to drill a new borehole that extends outside an existing wellbore, the usual practice is to use a work string to run and set a whipstock via an anchor disposed at the lower end thereof. The upper end of the whipstock comprises an inclined face. The inclined face is designed to guide a window milling bit(s) radially outwardly with respect to the main wellbore axis as the milling bit is lowered, so that the milling bit creates an opening in the main wellbore and into adjacent formation rock. The main wellbore may have casing cemented in place or be without casing, known in the art as “open hole.” The lower end of the whipstock is connected, directly or indirectly, to an anchor so that when the anchor is locked in the wellbore it prevents both axial and rotational movement of the whipstock.
Wellbore departure technology provides operators several benefits and economic advantages. For example, wellbore departure and lateral drilling operations can access isolated pockets of hydrocarbons which might otherwise be left in the ground. In addition, lateral drilling technology improves reservoir drainage, increasing the volume of recoverable reserves and enhancing the economics of marginal pay zones. Anchors are a key component of wellbore departure operations.
Some disadvantages of known wellbore anchors include limited radial expansion capabilities and limited force for securing the anchor against the wellbore wall, especially in larger diameter wellbores. As such, prior art expandable anchors that support whipstocks for drilling sidetrack boreholes, for example, may be susceptible to small, but not insignificant amounts of movement. Hence, it would be desirable to provide an expandable anchor that effectively prevents an anchored whipstock from moving.
Examples of such systems include U.S. Pat. No. 7,377,328, entitled “Wellbore Anchoring System” shows an expandable downhole anchoring tool positionable within a wellbore for use in cooperation with drilling equipment. That system includes a body having a plurality of angled channels formed into a wall thereof, and a plurality of moveable slips disposed in the same radial plane around the body. There, the plurality of moveable slips are hydraulically translatable along the plurality of angled channels between a collapsed position and an expanded position. The disclosure further encompasses a method of setting an expandable anchor within a wellbore and includes running the anchor into the wellbore in a collapsed position. Then, expanding the anchor into gripping engagement with the wellbore, the anchor adapts to expand up to at least 1.5 times a collapsed diameter of the anchor.
U.S. Pat. No. 8,919,431, also entitled “Wellbore Anchoring System” shows a hydraulic wellbore anchoring system for use with whipstocks or other tools in either cased or open hole wellbores. The anchoring system includes an upper slip system and a lower slip system. The anchor system may be set using hydraulic pressure and withdrawn by a predetermined upward force. While the slips of the upper and lower slip systems may be set substantially simultaneously, the anchoring system enables sequential disengagement of the slips to reduce the force required for withdrawal.
With the anchoring systems referenced above certain limitations exist. First of all, a limitation relates to the susceptibility to shocks that frequently occur as the anchor system traverses down the wellbore. Contact with an uneven wellbore, debris, and other irregular or unexpected interferences may arise as the anchor trips into the wellbore. In some situations, slips and inserts may contact these interferences during the trip into the wellbore and sustain damage. Damage to these components can adversely affect the performance of an anchor system, including anchor placement and stability in the wellbore. The unfortunate result may be an anchor system that is improperly positioned or insecurely placed. This could jeopardize the entire wellbore departure operation and result in significant losses in terms of non-productive time and monetary capital.
Another limitation with existing anchor systems is relatively weak setting force. Many known anchors employ a single means of applying setting force. Some known hydraulic anchors may have means for applying two different types of setting force, but may do so in sequence, not applying these forces concurrently. The ability to apply additive force, such as means of applying three or more types of setting force, is not seen in the prior art. The failure to use additive setting forces results in a less than secure anchor that sets with less certainty in the wellbore.
In light of these considerations and others, which are here addressed, there is the need for an improved dual-action hydraulically operable anchor system and methods of operation and manufacture as here described and claimed.